Next week, officials will bury a time capsule in a stairwell of the Manhattan Bridge with instructions to open in 2109.

But this isn’t your typical time capsule. It will contain a simple warning about avoiding disaster: Take care of your bridges, or else.

The Manhattan Bridge is the perfect venue for a time capsule with a moral message -- after all, the bridge could well have collapsed in the 1980s.

“We could have lost the entire Manhattan Bridge. The potential for mass catastrophe was great,” said Sam Schwartz, a city transportation commissioner who helped spearhead the rehab of the city’s crumbling bridges in the 1980s.

At its outset, the Manhattan Bridge was fraught with controversy. The city needed to ease crippling congestion on the Brooklyn Bridge, but officials couldn’t decide where another East River span should go and haggled over a dozen options. The city ended up extending Flatbush Avenue to the bridge, but had to cut through an old warehouse district. The $31 million structure was the city’s first true suspension bridge, but it was so svelte that it swayed as much as eight feet.

“It was critically important to build a bridge. But it had a very troubled history,” said Michael Miscione, the Manhattan borough historian.

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Known as “Bridge No. 3,” the Manhattan Bridge was always a stepchild to the Brooklyn and Williamsburg bridges, Miscione said. But it did include one of the most impressive entrances, with a stone archway styled after a similar arch in Paris.

“It’s a little bit of an acquired taste,” Miscione said.

Beginning in the 1940s, bridge maintenance was slashed across the city, with the neglect hitting epic proportions in the 1970s. When Schwartz took office in 1986, he immediately shut part of the Manhattan Bridge and cut subway service over it, as one of the four steel cables was precariously weak.

“Drivers were screaming bloody murder. It was a terrible time,” Schwartz said.

Nearly $1 billion and three decades later, the bridge is getting up to snuff, as are the city’s other major spans, Schwartz said. The Manhattan Bridge celebrated its 100th birthday last year, as did the Queensboro Bridge. But officials hope the time capsule, which will contain letters, reports and memorabilia, will help future generations remember the importance of regular upkeep.

“They were senior citizens for awhile, so they needed senior care,” Schwartz said. “They are out of (intensive care) and healthy again. One hundred is the new 50.”

Manhattan Bridge facts:- Carries about 375,000 people a day, the most of any city bridge

- Originally had two female statues representing Brooklyn and Manhattan at its base. The statues now flank the Brooklyn Museum

- Paved the way for sleeker suspension bridges such as the George Washington and the Verrazano-Narrows

- Partially designed by the same builder who made the Tacoma Narrows Bridge, which collapsed four months after being built